The present invention relates to a roller with an outer mantle and a hollow or solid inner shaft, the middle part diameter of the inner shaft being greater than that of its other parts and the outer mantle being joined to the middle part of the inner shaft by shrinking.
Paper machines and other similar machines have a great number of rollers which deflect under a load. The deflection disturbs the operation of the machine, and for this reason attempts are made to reduce or eliminate it. For this reason the conventional roller structure with a hollow cylinder which is supported by the shaft at both ends has been replaced by, for example, a structure in which the hollow cylinder is supported by the shaft at its middle part or close to it. The deflection of such an anti-deflection roller under a load is considerably less than that of a conventional roller.
The structure according to Finnish Pat. No. 45 777 can be mentioned as an example of an anti-deflection roller. This structure has a mantle shrunk over a solid or tubular central shaft so that when the roller, supported by the central shaft at the ends, is loaded, the mantle deflects at the middle part of the roller at the shrinkage joint according to the shape of the inner shaft. Outside the shrinkage joint the mantle is free and bends in the manner of a protruding beam. The durability of the shrinkage joint is poor owing to friction corrosion, and the roller is heavy and has a great diameter. In addition, it is difficult to obtain a straight roller free of warpage.
Also known is a structure according to FIG. 1 of the drawings. In this one, the steel mantle tubes have been welded to the inner shaft. It is more difficult to make the structure straight and warpage-free but it has a better loading capacity. Even in this one the inner shaft can be tubular, and a very light structure can be obtained. The welding of the mantle tubes, however, causes uneven pulling tension, and it is difficult to make the roller straight. If it is straightened by machining on the surface, an imbalance which is difficult to rectify is created.